1. Field of the Invention
This invention relates to a vibration-damping material with excellent workability in deep drawing, bending, etc.
2. Description of the Prior Art
In recent years, the influence of noises caused by transportation means such as automobiles, railroads and the like or of noises and vibrations generated at construction sites upon residents in the neighborhoods is becoming more and more serious incurring a big social problem. As one means for solving the problem, research and development on vibration-absorbing materials having a vibration-absorbing ability by themselves has been made, and as a result, vibration-damping materials having a large vibration-absorbing ability and suitable for various application purposes are already in use as structural members of vehicles, vessels, industrial machines, iron bridges, etc. As these vibration-damping materials, there have hitherto been known multilayer type structures using, for its middle layer, a composition such as vinyl acetate-ethyl acrylate copolymer (Japanese Patent Publication No. 35662/1970), a copolymer obtained by grafting a vinyl acetate-ethylene copolymer with a mixture of styrene and acrylonitrile (Japanese Patent Publication No. 17064/1971) or the like, materials composed of a bitumen and a filler such as calcium carbonate or the like, and so forth.
These vibration-damping materials each show a vibration-absorbing ability in a particular temperature range when made into a multilayer structure together with metal plates. However, such multilayer structures have various drawbacks such as poor deep drawing or bending in mechanical pressing (due to insufficient bonding with metal plates, small modulus of elasticity of middle layer composition, etc.), poor heat resistance and the like. Thus, they are insufficient in secondary workability as vibration-damping metal plates.
When the conventional vibration-damping materials were used in applications where they are immersed in an oil, such as oil pans of automobiles, parts of machine tools and the like, and when the materials were composed of a resin material poor in oil resistance, they apparently showed a low bonding strength with steel plates resulting in poor workability and/or insufficient vibration-damping ability.
The conventional vibration-damping metal plates have various drawbacks in workability in mechanical pressing, etc. For example, in deep drawing, metal plates cause slipping at the ends and, in an extreme case, two upper and lower layer metal plates come off a middle layer vibration-damping resin and cause separation. Further, the low elasticity of the resin layer causes problems such as surface waviness of shaped article, wrinkle formation at curved corner surfaces and the like. In severe 180.degree. bending (so-called hemming) which is applied to the ends of vibration-damping metal plates, waviness and wrinkle formation appearing at the surfaces of metal plates become more serious making these meatl plates unusable in practical application.